Electromagnetic interference, referred to as EMI, is any unwanted electromagnetic energy radiated from an electronic device. An electronic device, such as a printed circuit board or backpanel, which is not properly designed or shielded to protect against EMI emissions may generate EMI radiation which can compromise the operation of adjacent electronic devices. Likewise, the operation of an improperly protected device may be compromised by emissions received from external EMI sources or from EMI sources within the device itself.
The increase in electronic component clock frequencies and the adoption of increasingly stringent regulations in the United States and Europe governing EMI emissions has elevated the need to factor EMI considerations into the design and construction of electronic devices such as logic and circuit boards.
A printed circuit board or backpanel will have reduced EMI emissions when the edges of the board substrate must be sealed with metal. Several methods are known for edge sealing substrates, including: soldering of a metal foil strip around the edges of the substrate, plating metal onto the edges of the substrate, painting the edges of the substrate with conductive paint, or inserting a metal gasket around the edges of the substrate. The metal edging must connect to a ground plane within the substrate to properly insulate the substrate. Most of these methods suffer from disadvantages such as high cost or degraded performance, which may be caused by an air gap between the metal shielding and the substrate.